The invention relates to a knife roller drive, especially suited for paper shredders or other file destroyers. Such a drive, equipped with a partially free-wheeling or override clutch or coupling, is known, among others, from German Patent No. 16 11 752. This "override clutch" primarily serves the purpose of being adapted for supplying a sufficient amount of torque, in the case of an operational breakdown caused by the clogging or jamming of the material being cut. The override clutch also serves the purpose of supplying sufficient amounts of torque for the free-wheeling of the knife roller in reverse, as well as during the restarting process after the cleaning of the jam or clog in forward under load. The known speed or rpm reduction transmissions, having teeth belts and corresponding belt pulleys, have for the purpose of supplying a sufficient amount of torque a pin located at the end of a knife roller shaft which functions together with the belt drive pulley which pulley is located in the plane of the belt. The belt drive pulley is equipped with a stop with two stop surfaces. This known type of override or partially free-wheeling clutch or coupling may work satisfactorily with an rpm reduction transmission which utilizes belts with teeth. This type of override clutch, as described above, will not, however, work especially well with such reduction transmissions which primarily consist of gear wheels. Particularly gear wheels made from synthetic materials such as plastic and composites, for instance, such synthetically made gear wheels have gained more and more usage in mass production, thereby, creating a need for the invention embodied in such an arrangement as set forth below. One disadvantage of using a single pin in such a partially free-wheeling coupling would be the asymmetrical or uneven load placed on a synthetic gear wheel by the clutch or coupling pin which could distort or forcefully tilt the respective gear wheel against the pinion gear wheel, thus leading to sporadic or localized stress on the teeth of the synthetic gear wheel. This distortion of the gear and the tooth, making contact with the other gear, could result in an additional disadvantage which would be the increased wear and tear on the teeth, if not even total destruction of the synthetic gear teeth and/or wheel.
Another shredder with increased reverse unlocking torque is found in U.S. Pat. No. 4,545,537. Other patents which may possibly be of some interest are U.S. Pat. Nos. 4,034,918; 4,026,480: and 3,703,970.